When the windmill falls apart in this chapter, Napoleon blames Snowball. Napoleon blames him because Snowball has been designated as the enemy who is the cause of all the bad stuff. Napoleon needs a scapegoat like that because he cannot admit anything is his fault.

In this story, Napoleon has set up a system where he is like a god of sorts -- it's called a cult of personality. If he ever admits he's done something wrong, it will ruin his image and reduce his power. So when something bad happens, he blames it on Snowball and portrays himself as defending Animal Farm against Snowball and all the other enemies.

Napoleon blames Snowball because there are pig footprints coming away from the wreckage. Napoleon needed to create a common and absent enemy so that he would have someone to blame when things go wrong. Napoleon actually destroyed the windmill himself.